Well tool apparatus and method of operation



c. c. BROWN 3,409,081

WELL TOOL APPARATUS AND METHOD OF OPERATION Nov. 5, 1968 3 Sheets-Sheet 1 Filed May 18, 1967 LICERO 0.8 0W

INVEN FOR C. C. BROWN Nov. 5, 1968 3,409,031 WELL TOOL APPARATUS AND METHOD OF OPERATIOIA 3 Sheets-Sheet 2 Filed May 18. 1967 O E w! \A S Z ma i UH. m2 22 L H j,\ I $717 2 A? 4/ xi W HW a Q \Q Hll B o o o ATTORNEY Nov. 5, 1968 c. c. BROWN WELL TOOL APPARATUS AND METHOD OF OPERATION 3 Sheets-Sheet 5 Filed May 18, 1967 ATTORNEY United States Patent 3,409,081 WELL TOOL APPARATUS AND METHOD OF OPERATION Cicero C. Brown, Brown Oil Tools Inc., P.0. Box 19236, Houston, Tex. 77024 Filed May 18, 1967, Ser. No. 639,451 11 Claims. (166-35) ABSTRACT OF THE DISCLOSURE A tool string and its method of operation for enabling a plurality of operations to be performed in a well bore without removing the primary pipe string from the well bore. The tool string includes a drill pipe string carrying a two-part drill bit comprising a tubular main bit, and a pilot bit releasably mounted in the bore of the main bit for removal by other tools insertible through the drill pipe string and the bore of the main bit to enable pertormance of other operations, such as well perforating, by such other tools, all without requiring removal of the drill pipe string from the well bore.

Background of the invention In many operations in connection with the drilling of oil and gas wells, it is often necessary to perform various types of operations in the well bore, many of which may be termed repair operations which involve placing cement plugs in the well casing to seal up leaks or improperly located perforations. These must then be followed by drilling out the cement plug and reperforating or performing other operations necessary or appropriate to the procedures involved.

In conventional operations of the type described, a series of runs with drill pipe, tubing, or wire line strings must be made to introduce the succ ssive forms of tools required to perform the several operations which may be involved. Each time a string of pipe carrying well tools is run into and out of a well, a considerable amount of time is involved which can be very expensive, particularly where the operations must be conducted at great depths as is often the case.

For example, in a not uncommon situation where a well casing has be n perforated at a location which does not communicate with the producing formation, it is necessary to shut-off these perforations and reperforate at the correct locations, Closing off of the undesired per forations is generally done by packing-oifthe well bore at proper points and placing a body of cement in the well bore at a location such as to plug the incorrectly located perforations. Very often this is done under pressure to squeeze off the perforations. This operation requires the running of a string of pipe and other equipment, as may be required for placing the cement, and this equipment must then be removed from the well bore. Thereafter, as soon as the cement has hardened a drilling string carrying a drill bit must be run back into the well to drill out the cement plug to clear the bore hole. This string must then be withdrawn from the well and replaced by a pipe or wire line string carrying a perforating gun to reperforate the casing at the proper location.

Thus, it will be seen that several trips, requiring running and withdrawing pipe strings, must be made into and out of the well bore to complete the series of operations outlined above, all of which necessarily require a substantial amount of time which, in a conventional deep well drilling operation, is very costly.

Summary 0 the invention The present invention is directed to a tool string for use in a well bore and its method of operation by which a plurality of operations, such as those described above, may be performed in the well bore, using the same primary pipe string without having to withdraw the same from the well bore during the performance of the several operations being performed. i

In accordance with the present invention, the tool string comprises the combination of a drill pipe string carrying on its lower end a two-part bit comprising a main bit having an axial bore aligned with the bore of the pipe string, and a tubular pilot bit receivable in the bore of the main bit for movement entirely through the main bit in either direction. Means for releasably securing the pilot bit to the main bit is provided and arranged for connection to another well tool, which may be a perforating gun, insertible through the bore of the drill pipe string and which may be manipulated to release the pilot bit for movement downwardly out of the main bit, permitting the perforating gun or other tool to be lowered through the bore of the main bit to a point in the well at which it may then be actuated to perforate the well bore while remaining attached to the pilot bit. The latter may then be withdrawn with the attached tool through the main bit and the drill pipe to the surface to clear the bore of the pipe string and the portion of the well which has been perforated.

By use of this apparatus other operations may be conducted either before or after perforation. More particularly, the Well bore below the bit may be closed-off with the cement plug by employing the drilling string as a cementing string for placing the cement while the complete bit is in place on the lower end of the drill string and thereafter, after the cement has hardened, the drill string, including the bit, may be employed to drill out the cement plug prior to the running of a perforating gun or some other tool to be employed for performing some other operation in the well bore.

This invention includes the method or procedures by which the apparatus described may be employed to perform a plurality of operations in the well bore with a single primary pipe string without withdrawing the same from the well bore during the course of such operations.

Other and more specific objects and advantages of this invention will become more readily apparent from the following detailed description when read in conjunction with the accompanying drawing which illustrates the invention.

In the drawing, FIG. 1 is a longitudinal, partly sectional, view of an apparatus in accordance with this invention shown inside a well casing and in which the pilot bit is shown locked in place in the main bit;

FIG, 2 is a view similar to FIG. 1 showing a perforating gun secured to the pilot bit, the parts being shown in position at release of the pilot bit from the main bit;

FIG. 3 is a view showing the tool string, including the perforating gun, lowered through the main bit and following perforation of the wall of the well bore;

FIG. 4 is a view similar to FIG. 3 showing the pilot bit and erforating gun in the process of withdrawal through the main bit and supporting drill string;

FIG. 5 is a cross-sectional view taken along line 5-5 of FIG. 1;

FIG. 6 is a longitudinal sectional view through a well showing the entire assemblage with the perforating gun lowered to the position in the Well at which it is actuated to perforate the well wall; and

FIG. 7 is a perspective elevational view of the pilot bit employed in the apparatus in accordance with the illustrative embodiment of this invention.

Referring to the drawing, there is shown a portion of a well casing C which lines the wall of a well here W intersecting earth formations, including the formation F (FIG. 6). The primary tool string comprises a string of drill pipe P, to the lower end of which is connected a drill bit, designated generally by the letter B.

Drill bit B is a two-part structure comprising, a main bit, designated generally by the numeral 11. Main bit 10 includes a tubular body 12 having an axial bore 13 extending entirely therethrough and of substantially the same diameter as the bore of pipe string P. The upper end of body 12 is provided with internally threaded socket 14 for attachment to the lower end of pipe P. Body 12 carries a plurality of angularly spaced radially extending cutting blades 15 defining at their lower ends hard surface cutting teeth 16 surrounding the area defined by bore 13.

Pilot bit 11 comprises a tubular shank 17 having an axial bore 18 and carries on its lower end a plurality of angularly spaced radially extending cutters 19 disposed to drill out the section of a well not covered by teeth 16 and generally aligned with bore 13 of the main bit.

A releasable connection is provided between shank 17 and body 12 and comprises a plurality of angularly spaced latching dogs 20 mounted in radial windows 21 provided through the wall of shank 17 intermediate its ends and disposed therein for radial movement into and out of an annular latching groove 20a provided in the inner wall of bore 13 of the main bit.

A tubular expander sleeve 22 is co-axially inserted in bore 18 of the pilot bit shank and carries radially projecting expander lugs 23 abuttable with complementary lugs 24 mounted on the rear faces of dogs 20. The lugs are so arranged that when lugs 23 are disposed opposite lugs 24 they will urge dogs 20 radially outwardly into latching engagement with groove 20a and when moved upwardly or downwardly to a position out of registration with dogs 20, the latter will be released for retraction from groove 20a, whereby to release the pilot bit from its connection to the main bit. A bushing 25 is screwed into the upper end of shank 17 and slida'bly surrounds sleeve 22. The latter is initially held in latching position behind dogs 20, as shown in FIG. 1, by means of one or more shear pins 26 mounted in bushing 25 and screwed into the exterior of sleeve 22. The upper. end of sleeve 22 carries a conventional fishing neck 27 for connection to other well tools, as will appear subsequently.

In order to secure pilot bit 10 against rotation relative to main bit 12 while at the same time permitting axial movement of the pilot bit relative to the main bit after shear pins 26 have been released, the bit members are provided with a series of longitudinal splined connections comprising angularly spaced spline slots 28 formed in the inner wall of main bit body 12 in interspersed relation to the portions of groove 20a which are disposed to receive dogs 20, as best seen in FIG. 5. The exterior of shank 17 carries angularly spaced, outwardly projecting, longitudinally extending splines 29 adapted to have free sliding fit in spline grooves 28. The grooves and splines may be formed to have the dove-tail configuration seen best in FIG. 5, to maintain effective non-rotative connection between the pilot bit and the main bit. The upper and lower ends of spline grooves 28 are outwardly flared at 30 and 31, respectively, to function as guides for the splines 29 which have their upper and lower ends convergently bevelled at 32 and 33, respectively, to cooperate with the flared openings at the end of the spline grooves. These features of the spline connection elements are best seen in FIGS. 4 to 7.

In FIG. 2, there is shown a perforating gun 35 of any generally conventional form, carrying perforating elements, such as a shaped charge or bullets, indicated at 36, and carrying on its lower end a grasping tool, such as a conventional overshot 37, adapted to be projected over fishing neck 27 for attachment thereto, for applying an upward pull to sleeve 22, and having an abutment element 38 seatable on the upper end of fishing neck 27,

where-by to permit application of downward force against 4 sleeve 22 through the operating string T carrying perforating gun 35.

In order to release the pilot bit from the main bit, when it is desired to perform subsequent operations to remove the pilot bit either downwardly or upwardly, sufficient force may be applied either upwardly or downwardly throught the attached tool, such as perforating gun 35, to break shear pins 26 and free the pilot bit for such movement, for purposes which will appear subsequently.

In performing a series of operations with the tool string described, it will first be assumed that drill pipe P, carrying bit 10, as shown in FIG. 1, will be lowered into casing C through a wellhead H (FIG. 6) to a point below which it may be desired to plug the bore of casing C, to seal off cracks or perforations which are undesired and which must be closed-01f before the casing is re-perforated in a producing formation, such as formation F, shown in FIG. 6. When so positioned in the well, cement may be introduced through the bore of pipe string P and through the openings formed by the bores of sleeve 22 and pilot bit 18 to provide a body of cement in the casing below the bit sufficient to form the desired solid plug in the casing. The several procedures involved in this operation are entirely conventional in connection with the drilling of oil and gas wells and the details thereof do not form a part of this invention.

When the cement has set to form the plug, the drill pipe string may be rotated in the usual manner, causing bit B to drill out the plug to the desired point opposite formation F, and in this operation the drill string and bits perform the normal and generally conventional drilling operation, and the spline connection between main bit 10 and pilot bit 11 will assure the rotation of both bits as a unit.

When the cement plug has been drilled out, tool string T carrying perforating gun 3S and overshot 37 will be lowered through drill pipe P and connected to the upper end of releasing sleeve 22. Suflicient force will then be applied either upwardly or downwardly through overshot 37 to break shear pins 26, as best seen in FIG. 2, and the tool string will then be lowered sufficiently to permit release of dogs 20 from groove 20a. Thereupon, as best seen in FIGS. 3 and 6, tool string T, carrying perforating gun 35 and pilot bit 11, will be lowered through bore 13 of the main bit where the perforating gun will be actuated to perforate casing C to provide a number of openings 0 through the casing wall and into communication with formation F. It will be understood that tool string T may be a pipe string or a wire line; but, in any case, a string which can be inserted and manipulated within the bore of pipe string P.

When the perforating operation has been completed, the tool string T will be drawn upwardly and the bevelled ends of splines 29 will cooperate with the flared openings in spline grooves 28 to effectively align the splines on the pilot bit with the spline grooves in the main bit so as to permit the pilot bit, together with perforating gun 35, to be drawn upwardly through the bore of main bit 12, and carried to the surface so as to be clear of pipe string P for use as a production string, for passage of other tools, or for any other purpose as may be desired.

While the foregoing description illustrates the structure and operation of a system which employs a perforating gun as one of the tools capable of operating with the system described, it will be understood that tools other than a perforating gun may be similarly employed and operated through the bore of the pipe string to remove the pilot bit and allow such other tools to be operated in the well bore below the low end of the drill pipe string.

It will be understood that various changes and modifi cations may be made in the details of the illustrative embodiment of the apparatus and in the method described herein, within the scope of the appended claims but 'without departing from the spirit of this invention.

What I claim and desire to secure by Letters Patent is:

1. Apparatus for use in wells, comprising in combination:

(a) a drill pipe string,

(b) a two-part drill bit carried by said drill pipe string,

said bit including (c) a main bit having an axial through-bore,

(d) a tubular pilot bit coaxially mounted in said through-bore and dimensioned for movement therethrough in either direction,

(e) latch means releasably securing the pilot bit to the main bit,

(f) a well tool insertable through said pipe string and the bore of said main bit for performing operations in the well bore below the main bit, and

(g) means carried by said well tool connectable to said latch means and operable in response to manipulation of said -well tool to release said pilot bit from the main bit for movement therethrough With said well tool.

2. Apparatus according to claim 1, wherein said well tool is a perforating gun.

3. In apparatus for use in wells:

(a) a main bit attachable to a drill pipe string and including a body having an axial through-bore and carrying laterally extending cutters,

(b) a pilot bit having a tubular shank coaxially receivable in said bore and carrying cutter elements on its outer end, said pilot bit being movable axially entirely through said bore in both directions,

(c) latch means on said shank arranged to releasably secure the pilot bit to the main bit,

(d) an actuator sleeve slidably disposed in the bore of said shank for axial movement therein between a first position actuating said latch means and a second position releasing said latch means,

(e) means initially securing said sleeve to said shank in said first position and releasable therefrom by axial movement relative to said shank, and

(f) cooperating spline elements arranged on said shank and said body to permit said axial movement of the pilot bit through the bore of said body while preventing relative rotation therebetween.

4. Apparatus according to claim 3, wherein said spline elements comprise a plurality of vertically extending angularly spaced grooves in the wall of said through-bore, and cooperably shaped elongate splines longitudinally mounted .on the exterior of said shank, the ends of said grooves being outwardly flared and the ends of said splines being correspondingly tapered.

5. Apparatus according to claim 3, wherein said means initially securing said sleeve to said shank comprises frangible means.

6. In apparatus according to claim 3, means carried by said shank for attachment of an operating tool string insertable through the bore of the drill pipe string.

7. Apparatus according to claim 6, wherein said operating tool string includes perforating gun means adapted to pass through the bore of said body.

8. Apparatus according to claim 3, wherein said latch means include a plurality of angularly spaced latching dogs mounted in the wall of said shank for radial movement into and out of latching engagement 'with a dogengaging element in the bore of said body.

9. Apparatus according to claim 8, wherein said spline elements are angularly interspersed with said latching dogs.

10. A method of operating tools in a well bore, comprising:

(a) inserting into a well bore a drill pipe string carrying on its lower end a tubular drill bit having a hollow pilot bit removably mounted in the bore thereof,

(b) operating the drill pipe string and bit to perform one or more selected operations in the well bore,

(c) thereafter running an operating string carrying perforating gun means through the bore of the drill pipe string,

(d) connecting said gun means to said pilot bit,

(e) manipulating said operating string to cause said gun means to remove said pilot bit downwardly out of the bore of said drill bit and to lower said gun means through said bore to a selected position below said drill bit while retaining its attachment to said pilot bit,

(f) actuating the gun means to perforate the wall of the -well bore, and

(g) withdrawing the gun means and said pilot bit through the bore of said drill bit and said drill pipe string from the well bore.

11. A method according to claim 10, wherein said one or more selected operations include:

(at) introducing cement through said drill pipe string and bit into the Well bore below the bit to form a plug in the Well bore, and

(b) after the cement has hardened operating the drill pipe string and bit to drill out the plug.

References Cited UNITED STATES PATENTS 2,544,993 3/1951 Jackson -238 X 2,883,154 4/1959 Daniel 175-1 3,115,188 12/1963 Cochran et al 166224 3,117,636 1/1964 Wilcox et al 175-257 3,169,591 2/1965 Worthington et al. 175257 3,169,592 2/1965 Kammerer 175-257 3,241,624 3/1966 Rassieur 175257 DAVID H. BROWN, Primary Examiner. 

